SPDIF (coax) buzzing when mouse is moved

[Viper GTS]

I'm using my PC as a source for an external DAC and amp (Keces DA-131.1 to a Shanling PH-100). I've had this setup working for about two months, but recently after re-arranging my office I'm getting a nasty buzz when moving the mouse (USB). I was originally using the SPDIF output on my X-Fi with no problems. In an attempt to isolate the problem I tried the coax output on my P5Q Deluxe with the same results. I've managed to eliminate it by using the TOSLINK output on the P5Q, but ideally I would like to use the X-Fi for everything so I need to fix this.

What should I be looking at as a culprit? I've never had to deal with this kind of issue on a digital connection, but it's definitely related to the physical connection between DAC & source. It buzzes when connected even if digital output is disabled.

Viper GTS

 

[Rubycon]

Ground loop. Using optical (TOSLINK) breaks the ground loop hence no noise.

There is a difference in voltage potential of the GROUND (chassis frame) in the circuits your equipment is plugged into. Since you changed physical location the PC and DAC are probably connected to different branch circuits or an outlet that has a partial floating ground. (not good!)

 

[Viper GTS]

I'm familiar with the concept of ground loop (I had to use a coax isolator on my cable box) but I wasn't aware it would cause issues on a digital connection (particularly when the noise is only there during mouse movement). Although I guess it would make sense for it to be causing hum on the analog output...

I believe I am using a different outlet for everything now, I guess I could move it back to the original & see if it follows.

Viper GTS

 

[spidey07]

Viper, the outer shielding of coax is ground. It's one of the most common causes of a ground loop because people don't think it can be a source of a ground loop or potential difference.

 

[Modelworks]

This is one of the main reasons I went with speakers that have amplifiers with optical connection. No more pc contributions to my music

Could also give this a try:

http://www.monoprice.com/produ...id=2947&seq=1&format=2